1. Field of the Invention
The present invention relates to a flash taking camera having a program lens shutter wherein the opening movement of the shutter is effected slowly and the closing movement of the shutter is effected quickly.
2. Related Background Art
A conventional program lens shutter such as disclosed in the U.S. Pat. No. 4,426,145 generally has a shutter opening feature that the opening movement of shutter blades serving also as an aperture is effected slowly (about 15-30 ms) and the closing movement of the shutter blades is effected quickly (about 5 ms), as shown in a graph of FIG. 6(a) where the ordinate indicates "area of aperture" AS and the abscissa indicates "time" t.
In the lens shutter camera having such shutter opening feature, when taking a photograph by energizing an electronic flash device, a flashmatic control is effected. In this case, as shown in FIG. 6(b), while the shutter blades are opened, i.e., before the shutter is completely opened, a flash start signal S is sent to the electronic flash device by closing a synchronizing contact, thus energizing the electronic flash device. With respect to an object having low brightness or luminance, since there is the possibility of camera shake due to a slow shutter speed, the shutter speed is limited to a certain time limit so as not to be too long. Here, the flashmatic control means that the timing of the flash emission is so controlled that the flash emission is started when the lens shutter reaches a predetermined shutter opening determined by the object distance and a guide number.
However, when shutter speed is limited as stated above, if an object field includes a low luminance object such as a night view, lamp, candle or the like, as well as a main object such as a person, such low luminance object is not so clearly taken, but only the main object which receives the flash light is clearly taken, thus providing an unnatural picture in which the main object floats on a black background.
In order to eliminate such drawback, recently, a lens shutter camera having a so-called slow synchronizing mode wherein the flash is emitted synchronously with a relatively slow shutter time has been proposed. However, in such lens shutter camera, since the timing of the flash emission of the electronic flash device is set at a point in the period when the shutter blades are being opened, when a moving light spot such as head lamps of a moving vehicle is taken, since the electronic flash device is emitted or energized at the beginning of the exposure period to expose the body (vehicle) for generating the light spot (head lamps) and there is a relatively long time from the energization of the electronic flash device to the full open state of the shutter, an unnatural picture in which there are traces of the head lamps ahead of the vehicle will be obtained.
In order to eliminate such drawback, it can be considered that the electronic flash device be energized during the closing movement of the shutter blades by utilizing a second blind (trailing blades) synchronism in a single lens reflex camera. However, in the shutter opening feature of the conventional lens shutter camera, as apparent from FIG. 6(a), since the closing movement of the shutter is very fast (as 5 ms), it is very difficult to control the timing of the flash emission, and, thus, such technique has not yet been realized.